It is known that lubricating oil in jet engines begins to coke especially in bearing chambers when the temperature exceeds 500.degree. F. This especially becomes a problem when, at engine shut-down, there occurs a soak-back of energy into the bearing chamber which acts to elevate the oil temperature. The prior art has attempted, in various ways, to reduce operating oil temperatures so that, during soak-back, coking does not occur. In addition to employing conventional radiator-type oil coolers, the prior art describes turbines wherein lubricating oil traverses radially through guide vanes of a jet engine to both cool the oil and provide for de-icing of the vanes. (e.g. see U.S. Pat. No. 2,474,258 to Kroon). In U.S. Pat. No. 2,439,447 to Buck et al, a turbine engine is shown in which radial struts communicate with a bearing chamber in the high temperature zone of an engine. The struts supply both oil and cooling air into zones surrounding the bearings.
In fan type, gas turbine engines, it is known (see U.S. Pat. No. 3,830,058 to Ainsworth) to utilize the air foil struts supporting the fan shroud as a path for accessory components (e.g., electrical, air and oil lines). For weight considerations, the shroud struts are hollow and the oil lines placed therein are surrounded by air spaces which provides an insulating barrier between the oil lines and the strut walls. This reduces the effectiveness of the cooling.
Accordingly, it is an object of this invention to provide an improved oil cooling system for a fan-type gas turbine engine.
It is another object of this invention to provide an improved oil cooling system for a fan-type gas turbine engine wherein advantage is taken of portions of the engine which lie in relatively cool air paths.